The present invention generally pertains to cannulas. More particularly, but not by way of limitation, the present invention pertains to cannulas for the removal of punctal plugs that are often used to treat dry eye syndrome, and to cannulas for the removal of obstructions from the lacrimal canaliculi.
FIG. 1 illustrates the lacrimal duct system of a mammalian eye 10. The system includes a lower punctum 12 connected to a lower lacrimal canaliculus 14, and an upper punctum 16 connected to an upper lacrimal canaliculus 18. Canaliculi 14 and 18 are connected to a lacrimal sac 20 and a nasolacrimal duct 22. A lacrimal gland 24 is connected to eye 10 via a lacrimal duct 26. In general, tears are produced by lacrimal gland 24 and are provided to eye 10 via lacrimal duct 26, and tears are drained from eye 10 via punctum 12 and canaliculus 14, punctum 16 and canaliculus 18, and nasolacrimal duct 22.
By way of background, tears produced by lacrimal gland 24 are actually a complex composition in the form of a tear film. This tear film includes three basic layers: an outer lipid layer, an inner mucin layer, and an aqueous layer between the lipid and mucin layers. Each of the layers has a particular function. The lipid layer prevents evaporation of the tears from the surface of eye 10. The aqueous layer provides oxygen to the cornea and contains additional chemical components that are important to a healthy eye 10. The mucin layer provides for interaction between the lipid layer and the aqueous layer and prevents tears from xe2x80x9cbeading upxe2x80x9d on the cornea.
Approximately 7.5 million cases of moderate or severe dry eye syndrome occur in the United States each year. An additional five million people are unable to wear contact lenses because of insufficient amounts of tear fluid. A xe2x80x9cdry eyexe2x80x9d is one that experiences insufficient lubrication of the cornea as a result a disturbance in the normal tear film. The condition encompasses a wide variety of disease states ranging from mild, intermittent burning and/or scratchiness with foreign body sensation, to a severe lack of aqueous layer secretion accompanied by corneal and conjunctival disease (keratoconjunctivitis sicca (KCS)). Dry eye can have a variety of specific causes and contributing factors, including arid environments, environmental airborne pollutants, certain systemic medications, auto-immune disorders, drug toxicity, hormone deficiency or changes, and even contact lens wear. However, the majority of cases of dry eye syndrome are related to two basic causes. First, lacrimal duct 26 from lacrimal gland 24 may become clogged or may malfunction so that an insufficient amount of tears reach eye 10. In response to this cause, artificial tear products such as TEARS NATURALE(copyright) and BION(copyright) TEARS, sold by Alcon(copyright) Laboratories, Inc. of Fort Worth, Tex., were developed. Second, although lacrimal gland 24 and lacrimal duct 26 may deliver a sufficient amount of tears to eye 10, tears may be drained away from eye 10 too quickly, creating a dry eye situation. In response to this cause, various methods and apparatus for sealing puncta 12 and 16 have been developed.
Initially, puncta 12 and 16 were sealed by stitching or by electrical or laser cauterization. Although such procedures can provide acceptable results, they are not reversible without reconstructive surgery. As it is sometimes difficult to determine whether dry eye is caused by too great of drainage or too little tear production, such procedures may expose the patient to unnecessary trauma. In addition, such procedures may result in epiphera, a condition where tears continually form on eye 10, build up, and run down the face of the patient.
Pre-formed collagen plugs for insertion into puncta 12 and 16 or the canaliculi 14 and 18 were developed to provide a reversible sealing procedure. Collagen plugs are water-soluble and, when inserted into the puncta, typically dissolve within seven to fourteen days. Collagen plugs are thus effective as a test procedure to determine if it is desirable to more permanently seal the puncta.
Pre-formed water-insoluble plugs for insertion into puncta 12 and 16 or canaliculi 14 and 18 are described in a variety of United States Patents. For example, U.S. Pat. No. 3,949,750 to Freeman describes such a plug having a head portion that extends outside of the punctum and a barb portion that extends into the punctum and/or canaliculus. Such plugs can be seen in the corner of eye 10, are sometimes uncomfortable, and are easily dislodged. In addition, such plugs are somewhat difficult to insert, and occasionally their size and shape causes tissue damage during insertion. If such plugs protrude too far from the puncta, they can cause irritation to the sclera. Furthermore, the tissue of the punctum can be damaged due to prolonged dilation caused by such plugs. U.S. Pat. No. 5,283,063 to Freeman describes a similar plug made from a hydrogel material having a hydrating port located in its barb portion that allows canalicular fluid to enter the barb and hydrate the plug to an expanded, relatively flexible state. U.S. Pat. Nos. 5,723,005 and 5,171,270 to Herrick describe water-insoluble punctal plugs that have collapsible flared sections for improved sealing and anchoring within the canaliculus. Some of these plugs also have a retaining portion that extends outside the punctum to further anchor the plug and prevent migration down the canaliculus. U.S. Pat. Nos. 3,949,750; 5,283,063; 5,723,005; and 5,171,270 are each incorporated herein by reference.
In addition, U.S. Pat. No. 5,469,867 to Schmitt describes a method of occluding the lacrimal canaliculi and other mammalian channels or ducts by injecting a heated, flowable polymer or polymer composite of a specified composition through puncta 12 and 16 into canaliculi 14 and 18, respectively. The specified polymer and polymer composite are non-immunogenic, biocompatible materials that are solid and/or non-flowable at body temperature or lower and flowable when heated slightly above body temperature. The polymer and polymer composite are capable of quickly changing from a flowable state to a non-flowable state by moving through only a few centigrade degrees of temperature. After injection, the polymer or polymer composite cools and solidifies to form a plug that conforms exactly to the geometry of the canaliculi. U.S. Pat. No. 5,469,867 is incorporated herein by reference, and the plugs for occluding the canaliculus or other mammalian channels disclosed therein will be referred to in this document as xe2x80x9ccast-in place thermoplastic plugsxe2x80x9d.
As mentioned above, it is highly desirable that a punctal plug be removable without the necessity of surgery. Various conventional techniques have been utilized to remove the above-described water insoluble plugs. For example, such plugs that have a portion extending outside the punctum are typically removed using forceps or a similar instrument.
As another example, certain cannulas have been used to xe2x80x9cflushxe2x80x9d water-insoluble plugs not having a portion extending outside the punctum down nasolacrimal duct 22. More specifically, it is known to use a cannula having an outer diameter equal to or slightly greater than the diameter of punctum 12 to seal the punctum and then inject saline into the punctum. The seal is created by dilating the punctum with the cannula and the sphincter action of the punctal muscle tightening around the cannula. Saline is then injected into canaliculus 14 so as to create enough water pressure to flush the plug down nasolacrimal duct 22. An example of a conventional cannula that has been utilized to perform this technique is the E4404 lacrimal cannula sold by STORZ Ophthalmics of St. Louis, Mo., which has a 23 gauge outer diameter, 10 mm long tip.
It is also known to use a cannula having a smaller outer diameter distal tip (e.g. 26-27 gauge) that tapers into a larger outer diameter proximal portion (e.g. 23 gauge or greater) to perform a similar flushing procedure, such as the cannula disclosed in U.S. Pat. No. 5,593,393 to Trudell et al. When such a cannula is inserted into punctum 12 beyond the taper, the larger outer diameter proximal portion dilates punctum 12, and the sphincter action of the punctal muscle tightens around the proximal portion to complete the seal. Saline is then injected into canaliculus 14 so as to create enough water pressure to flush the plug down nasolacrimal duct 22.
However, dilation of the punctum can be dangerous, and prolonged dilation of the punctum can damage punctal tissue. In addition, due to the difference in sizes of a particular patient""s punctum, such as, by way of example, the difference between a male adult human being, a female adult human being, and a child human being, cannulas with various outer diameters may be required to effectively create the above-described punctal seals.
Finally, it is known to use a cannula with an outer diameter less than the diameter of punctum 12 (e.g. 27 gauge) to flush such water-insoluble plugs down nasolacrimal duct 22. Such a cannula can be inserted into punctum 12 without dilation, but does not seal the punctum. Saline is then injected into canaliculus 14 in an attempt to create enough water pressure to flush the plug down nasolacrimal duct 22. However, such a cannula typically does not create enough water pressure to flush the plug due to the lack of a punctal seal, and excess saline is xe2x80x9cbackflushedxe2x80x9d out of the eye and down the patient""s face.
U.S. Pat. No. 5,469,867 discloses several techniques for removing its cast-in place thermoplastic plug from canaliculus 14. The plug may be physically extracted from the canaliculus by forceps or a similar instrument, or the plug may be heated by application of an electrical heating device that melts the polymer. In addition, a lipophilic compound such as a naturally occurring oil or fatty acid ester that dissolves into the polymer and reduces the melting point of the polymer below body temperature may be introduced into canaliculus 14 for plug removal. This technique transforms the plug into a flowable fluid that is removable by irrigation with saline solution, which is typically performed using one of the above-described cannulas.
Therefore, a need exists in the ophthalmic industry for an improved cannula for the removal of punctal plugs that are used to treat dry eye syndrome, and for the removal of obstructions from the lacrimal canaliculi, that does not suffer from the above-described problems. The improved cannula must be easy to use, safe for the patient, and capable of economic manufacture.
The present invention pertains to improved punctal cannula and methods of using such cannula to remove plugs or obstructions from mammalian canaliculi. More particularly, one aspect of the present invention comprises a cannula including a body having a distal portion, an external annulus disposed proximate the distal portion, and a hollow bore for fluid delivery from the distal portion. The distal portion is capable of insertion into a mammalian punctum without dilating the punctum. The external annulus has geometry capable of forming a seal with an external surface of the punctum without dilating the punctum.
In another aspect, the present invention comprises a method of dislodging a plug or an obstruction from a mammalian canaliculus having a punctum. A cannula including a body having a distal portion, an external annulus disposed proximate the distal portion, and a hollow bore for fluid delivery from the distal portion is provided. The distal portion is inserted into the punctum without dilating the punctum. The punctum is sealed by contacting an external surface of the punctum with the external annulus without dilating the punctum. An ophthalmic fluid is injected into the punctum with the cannula to pressurize a portion of the canaliculus between the plug or obstruction and the punctum.
In another aspect, the present invention comprises a lacrimal cannula including a body having a distal portion, an external annulus, and a hollow bore for fluid delivery from the distal portion. The external annulus has a generally spherical geometry with the distal portion extending axially therefrom. The distal portion is capable of insertion into a mammalian lacrimal punctum without dilating the punctum. The external annulus is capable of forming a seal with an external surface of the punctum without dilating the punctum.
In another aspect, the present invention comprises a lacrimal cannula including a body having a distal portion, an external annulus, and a hollow bore for fluid delivery from the distal portion. The external annulus has a generally inverted-cone shape geometry with the distal portion extending axially from a tip toward a base of the cone. The distal portion is capable of insertion into a mammalian lacrimal punctum without dilating the punctum. The external annulus is capable of forming a seal with an external surface of the punctum without dilating the punctum.
In another aspect, the present invention comprises a lacrimal cannula including a body having a distal portion, an external annulus, and a hollow bore for fluid delivery from the distal portion. The external annulus has a generally cone shape geometry with the distal portion extending axially and outwardly from a tip of the cone. The distal portion is capable of insertion into a mammalian lacrimal punctum without dilating the punctum. The external annulus is capable of forming a seal with an external surface of the punctum without dilating the punctum.
In a further aspect, the present invention comprises a method of removing a cast-in place thermoplastic plug from a mammalian lacrimal canaliculus having a punctum. A cannula including a body having a distal portion, an external annulus, and a hollow bore for fluid delivery from the distal portion is provided. The distal portion extends axially from the external annulus. The distal portion is inserted into the punctum without dilating the punctum. The punctum is sealed by contacting an external surface of the punctum with the external annulus without dilating the punctum. A warm ophthalmic fluid is injected into the punctum with the cannula to pressurize a portion of the canaliculus between the cast-in place thermoplastic plug and the punctum to dislodge the plug.